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Should Aromatase-Inhibitor Adjuvant Therapy be Extended?

N Engl J Med; ePub 2016 Jun 5; Goss, Ingle, et al

Significantly higher rates of disease-free survival and a lower incidence of contralateral breast cancer was observed in women treated with an extension of an adjuvant aromatase inhibitor (letrozole) to 10 years compared to placebo, according to a recent study. However, the rate of overall survival (OS) was not higher with the aromatase inhibitor than with placebo, the study found. The trial enrolled 1,918 women with a median follow-up of 6.3 years. Researchers found:

• There were 165 events involving disease recurrence or the occurrence of contralateral breast cancer (67 with letrozole; 98 with placebo) and 200 deaths (100 each group).

• 5-year disease-free survival rate was 95% with letrozole and 91% with placebo (HR for disease recurrence or the occurrence of contralateral breast cancer, 0.66).

• The rate of 5-year OS was 93% with letrozole and 94% with placebo (HR, 0.97).

• The annual incidence rate of contralateral breast cancer in the letrozole group was 0.21% and in the placebo group, 0.49% (HR, 0.42).

• Bone-related toxic effects occurred more frequently among patients in the letrozole group.

Citation: Goss PE, Ingle JN, Pritchard KI, et al. Extending aromatase-inhibitor adjuvant therapy to 10 years. [Published online ahead of print June 5, 2016]. N Engl J Med. doi:10.1056/NEJMoa1604700.